The fight starts with Sin away from the ship preventing you from using close range attacks. Each turn the ship will draw by closer eventually allowing you to attack Sin from close by as well. Sin itself won't move until roughly 15 turns have passed after which he'll use the only available move in his arsenal Giga-Graviton.

If I remember correctly, I saved my Aeon's Overdrives for the end of the battle to quickly finish him off. The rest of the battle was fought the usual way, dish out as much damage as possible through physical attacks and heal only when necessary.

Logged

"Most people think time is like a river that flows swift and sure in one direction, but I have seen the face of time, and I can tell you - they are wrong." ~ Prince of Persia

Possessing Anima or Yojimbo will decrease the difficulty of this protracted battle.

I'm always sure to have Rikku's overdrive at full before I enter. Trio of 9999 is a godsend. Auron using Banishing Blade is another option. Sin has no resistance to Armour or Mental Breaks. Follow up with Quick Hits and Doublecasts. No defensive tactics are necessary so DO NOT HEAL. Hastega is a must though. If you're curious about a move's usefulness on balance with time, check the turn list at the top right. Standard parties will only JUST manage to knock off the last of his HP before he decides to use Giga-Graviton.

Logged

When the darkness of the Abyss threatens the world, the Phoenix will rise amidst a whirlwind of fire and light.

My best way for dealing with this fight was to get Wakka's Attack Reels Overdrive then have him and Rikku's Overdrive bars full when the fight starts.

Have Rikku mix for Trio of 9999 (I think you can use two Wings to Discovery to get it)

Then make sure you're at your best with the Attack Reels. If I recall correctly, getting "2 Hits" on every reel will have him attack 12 times. 12 * 9999 = 119,988. Not quite the full 140k, but getting him down to 20k in just two player moves is a good start!

Logged

Push the button. That's why it's there. If it wasn't meant to be pushed, it wouldn't be a button.